Federal investigators Thursday executed a new search warrant at Keller's home. Sources tell Team 5 Investigates Sean Kelly while viewing video tapes taken at that time, an investigator noticed a man's hand near the camera lens along with a unique watch.

They were able to get the date of the video featuring young boys that was taken at a resort in France. Sources say the video was shot during a time in which investigators believe Keller was overseas.

Federal investigators are searching for the unique watch seen in the video recovered from Dr. Keller's house a few months ago.

Keller was indicted in December on two counts of receiving child pornography and one count of possessing child pornography. The indictment says Keller obtained depictions of minors in sexually explicit conduct, including boys from about 7 to 16 years old.

Authorities alleged Keller had child porn delivered to him at Phillips Academy campus before his 2011 resignation.

Keller was arrested in September on a charge of receiving child pornography. He's been jailed since after voluntarily agreeing to detention.

Keller worked at Boston Children's Hospital and taught at Harvard Medical School.